The long-term objectives of this project are to develop in vivo and in vitro models for cutaneous lupus and to use these models to study the biology of cutaneous lupus. The athymic BALB/c mouse with grafted human skin was chosen as a potential animal model for cutaneous lupus. It has already been demonstrated that IgG from the sera of patients with photosensitive cutaneous lupus, injected intravenously (IV) into the nude mouse, will specifically bind to the human skin graft. These sera injected were "monospecific" for anti-SSA antibodies, autoantibodies strongly associated with photosensitive cutaneous lupus. In the proposed model for cutaneous lupus, the human skin graft on the nude mouse will be exposed to ultraviolet (UV) light in the UVB and UVA ranges. The mouse will be injected IV with serum from a patient with photosensitive cutaneous lupus, then injected IV with human monocytes and lymphocytes or subsets thereof. Tissue injury will be determined by gross and microscopic changes compatible with cutaneous lupus. After an animal model for cutaneous lupus is developed, the model will be analyzed in detail to determine which components of the model are important in the development of skin disease. To aid in determining if an antibody of a particular specificity is required, a monoclonal anti-SSA antibody will be used. To study the contributions of lymphocytes and monocytes, cellular infiltrates in the grafts will be examined with monoclonal antibodies to cell surface antigens. In addition, specific subsets of lymphocytes or monocytes will be injected. To study the effects of UV light, animals each with 4 human skin grafts will be given different doses of UV light to each graft, and effects of UV light on antigen, antibody, and cells will be measured. Complementary to the animal model, an in vitro model using human basal keratinocytes cultured in serum-free medium will be developed. In this system antibody-dependent cell-mediated cytotoxicity and complement-mediated cytotoxicity will be compared as mechanisms for damaging basal keratinocytes, and the effects of UV light will be further studied. The ultimate goal of this work is a clearer understanding of the pathophysiology of cutaneous lupus.